The present invention relates to a system for extracting the friction-generated heat from a preloaded roller bearing before the heat migrates into the bearing itself and surrounding components of the associated machine. More particularly, the invention is directed to a system which can maintain bearing temperature within an extremely narrow range, usually less than +/-1/2.degree. F. during operation of the associated machine.
Heat is mechanically generated by bearings during their operation due to friction and interference fit from preloading between the bearing elements. This mechanically generated heat is capable of raising the temperature of the bearings to a level where the bearing elements will become strained and deformed thereby adversely effecting the life of the bearing and the machine, as well as the accuracy of the machine. The heat generated by the bearings will also be conducted to other parts of the machine thereby causing additional deleterious effects to the operation and accuracy of the machine.
While bearings may be cooled to avoid the adverse consequences of overly high bearing temperatures, the over-cooling of bearings may also have adverse consequences on the operation of a machine. Over-cooling of a bearing will effect the fit between the bearing elements causing changes in the axis of rotation of the rotating member. Over-cooled bearings will also conduct heat away from adjacent areas of the machine thereby causing changes in the fit between other parts of the machine.
The present invention is particularly well suited for a two cylinder rotary die cutter which cuts or perforates material passing between two rotating cylinders. Such a machine requires that close tolerances be uniformly maintained between and along the length of the rotating cylinders for proper operation. Over-cooling or over-heating the bearings supporting each rotating cylinder can cause changes in the location of the axis of rotation of the cylinder which in turn effects the tolerances between the cylinders. The over-cooling or over-heating of the bearings will also cause heat to be conducted towards or away from other parts of the machine, such as the ends of each cylinder thereby causing a nonuniform expansion or contraction of the cylinders and adversely effecting the machines operation.
Various devices and systems have been used to absorb or dissipate the heat generated by bearings thereby cooling the bearings. These prior devices have been used to maintain the bearing temperature below a maximum temperature. Such devices are shown in the U.S. Pat. Nos. 2,173,489; 2,346,805; 2,755,989; 4,027,928; and 4,402,559. Other devices have been used to cool a rotating cylinder. Such devices are shown in U.S. Pat. Nos. 2,748,863; 3,359,974; and 3,707,012. However, none of these devices disclose a system in which the bearing temperature may be regulated and maintained at a desired temperature, or within a desired range of temperatures.